refactor: remove ratelimiting functionality,

add on-demand global / per-domain ddos protection enabling
add automatic redirect from captcha page back to the requested source
prettify the captcha page

src/libs/utils.lua

@@ -0,0 +1,18 @@
+local _M = {}
+local md5 = require("md5")
+
+function _M.get_hostname()
+    local f = io.popen ("/bin/hostname")
+    local hostname = f:read("*a") or ""
+    f:close()
+    hostname =string.gsub(hostname, "\n$", "")
+    return hostname
+end
+
+function _M.get_floating_hash()
+    -- This ensures that a cookie is rotated every day
+    return md5.sumhexa(_M.get_hostname() .. os.date("%d"))
+end
+
+return _M
+